Add console.error assertion to Web IDE feature spec

MR:

• Test: Add coverage to Web IDE spec for Workflow... (!162487 - merged)
• Test: Add BrowserConsoleHelpers for Capybara (!162499 - merged)

Description

The Web IDE recently failed some downstream QA tests, which could have been caught earlier if there were assertions that no console.error thrown.

• gitlab-com/gl-infra/production#18371 (closed)

Acceptance Criteria

• Let's add an assertion that no unexpected console.error messages are logged in our current Web IDE feature spec.
• We probably need to ensure the ability to ignore a set of messages.
• BONUS: Maybe we can add a test that the GitLab Workflow icon shows up.